This invention relates to automatic manufacturing equipment used for assembly and/or processing of products. More particularly, it relates to a high rate, flexible, automatic production system employing one or more robotic modules, each having a programmable servo-driven actuator, where each actuator is combined with slides mounted in guide rails that are part of an extruded structural frame to provide single direction linear robotic motion.
Current automated assembly or processing equipment for special products is typically custom tailored to one or more specific products, and designed to provide positioning or placement for end effectors or tools. Such automatic machines or systems consist of product feeding equipment (feeders, conveyors, magazines, trays etc.) and transfer equipment to move and position product from station to station. Several well-known transfer systems have been employed in automatic assembly. Transfer system types include rotary dial, indexing conveyor, indexing chain, belt, walking beam or palletizing conveyor, that work in combination with stop and lift/register devices.
A typical automatic assembly system may also employ so-called “positioning” or “placement” devices that utilize many different types of actuators. An actuator is a displacement device that activates, or repositions by force, a movable member of the machine, and may, for example, be pneumatic cylinders (compressed air operated), hydraulic cylinders (compressed fluid operated), or electrical motors in combination with belts, chains, gears or feed screws. The positioning device actuators are generally used to provide a so-called “pick and place” motion to the movable member. They can be used to retrieve a product from a feeding device and place the product onto a transfer device.
Sometimes the pick and place devices rely on the use of a cam-driven actuator to provide controlled acceleration/de-acceleration and achieve high speed for product placement. Such devices have a number of limitations and drawbacks. A rotating cam action typically is limited to a single position for points of pick-up and placement. Yet, more significantly, because its shape defines all motion parameters and cannot be changed quickly, a cam is limited to a single movement pattern. Thus, while a cam actuation device can provide fast product transfers, it cannot be used for more than a single point-to-point transfer without substantial modification.
Pneumatic cylinders are low cost and widely used in automated assembly machinery. However, this type of device generally doesn't have programmable position control or programmable acceleration and velocity. Thus utilization of pneumatic cylinders is limited to simple pick and place movements using mechanical stops for registration. The individual cylinders cannot be reprogrammed. Hence, these devices cannot be automatically changed for different positions. In addition, pneumatic cylinders exhibit high failure rates due to wear and require extensive maintenance, including repeated mechanical adjustments to control accurate position.
Pneumatic cylinders also suffer from an inability to maintain constant acceleration and velocity. This is due to the large number of variables that impact the function of the cylinders, such as: friction (lubrication), temperature fluctuation, air pressure fluctuation, air flow fluctuation, air leakage, moisture content in the air lines, wear of seals, bushings, and bearings, and contaminants inside the cylinder. Thus, application of this device is limited to pick and place or simple positioning of a tool when both pick up and destination points are fixed.
A servo-controlled robotic device is generally more expensive and frequently custom designed to include a complete device that is built with its own support and mechanical guiding means and a programmable controller for a single or several devices. Several standard linear robotic devices, manufactured by robotic companies are available as self-enclosed and fully integrated linear robotic modules. They can be mounted together to construct one-, two- or three-axis robots typically controlled by a single controller. Frequently such devices have performance that allows completion of motion with programmable control for acceleration/deceleration, velocity and position. However, the cost of these devices is high and often precludes their use due to high level of investment. It is known that high cost of investment in equipment frequently cannot be justified based on the benefit it produces.
For many products the manufacturing and assembly processes consist of many different steps, involving a large number of specialty parts. This makes standardization of the manufacturing robotics difficult. Many attempts have been made to create a standardized, programmable robotic device or system, that can provide a more cost effective and flexible approach to this dilemma. Such a system must be capable of being used for more then one application, with enough flexibility to manufacture more then one product.
The robotic devices are readily available to allow creation of such systems, but at a relatively high cost. The costs of such systems, in fact, are often so high as to outweigh the potential benefits of implementing dedicated automatic manufacturing systems.
The ability to create a low-cost programmable, servo-driven, multi-axis robot and construct modular automatic systems based on such robots is extremely important to the manufacture and assembly industry, and can provide substantial economic benefit.